Do not scoop the flour out of the container/bag with your measuring cup because you could end up with 50% more than you need. Rather, using a spoon, scoop the flour into the measuring cup. Do not pack the flour down and do not tap the measuring cup as both cause the flour to settle in the cup. After you’ve spooned the flour into the measuring cup, use the back of a knife to level off the top of the measuring cup.

If a recipe calls for “1 cup of flour, sifted”—measure the flour, then sift it. If a recipe calls for “1 cup of sifted flour”—sift the flour then measure. It all depends where the word “sifted” is in the ingredient wording. If “sifted” is before the ingredient name, sift before measuring. If “sifted” is after the ingredient name, sift after measuring.

• Source: https://sallysbakingaddiction.com/how-to-measure-baking-ingredients/